JP2003217977A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor of low impedance which has superior low-temperature characteristics and lifetime characteristics. <P>SOLUTION: The electrolytic solution of the electrolytic capacitor contains an electrolyte, water, and an electrolytic solvent containing organic solvent, with the water concentration in the electrolytic solvent being 20 wt.% to less than 35.3 wt.%. The organic solvent can contain at least one kind selected from among protonated solvent and non-protonated solvent. At least one kind selected out of carboxylic acid or its salt and inorganic acid or its salt can be contained as the electrolyte in the electrolytic solution. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor having low impedance, excellent low temperature characteristics, and good life characteristics.

[0002]

2. Description of the Related Art Generally, an electrolytic capacitor is formed by etching a high-purity aluminum foil to increase its surface area, and then anodizing the surface to make it a dielectric, and an etched cathode foil facing the anode foil. An element having a structure in which a separator (electrolytic paper, separator paper, or the like) is wound between and is impregnated with an electrolytic solution, and is enclosed in a case.

Since these conventional aluminum electrolytic capacitors have electrolytic paper impregnated with an electrolytic solution, the impedance characteristics of the capacitors tend to be high. In order to improve the impedance characteristic, measures such as lowering the resistance of the electrolytic solution itself, thinning the electrolytic paper, or lowering the density have been studied.

However, when the resistance value of the electrolytic solution is lowered, the reactivity between the aluminum foil and the electrolytic solution is increased and the life characteristics are deteriorated. On the other hand, when the separator (electrolytic paper) is simply thinned or the density is lowered. The tensile strength is lowered, the shape retention is lowered, and problems such as damage in the manufacturing process such as winding of the capacitor and a decrease in productivity occur. Further, as a result, problems such as an increase in short circuit defect rate occur.

Further, by using cellulose fibers such as wood kraft pulp, coniferous wood pulp and Manila hemp pulp, hydrogen bond between fibers and entanglement of fiber fibrils are used to improve tensile strength and shape retention. However, as a result, attempts have been made to reduce the thickness of the separator (electrolytic paper), but even in that case, in order to further improve the performance to meet the more stringent requirements for impedance characteristics, the density of the separator should be reduced. If the thickness is made lower and the thickness is made thinner, the same problem as described above will occur, so there is a limit.

[0006] A method is known in which thermoplastic fibers such as polyethylene fibers, polypropylene fibers and nylon fibers are mixed in the raw material to make paper, and then the thermoplastic fibers are fused to increase the tensile strength. In addition to the fibers, artificial fibers such as viscose rayon fibers, polypropylene fibers, polyimide fibers, and aramid fibers, synthetic fibers, glass fibers, and inorganic fibers such as alumina-silica fibers are mixed with strong fibers to secure the strength. Low density, thin,
And, it has been attempted to obtain a separator (electrolytic paper) having a high porosity, but, for example, when a thermoplastic fiber is used, it becomes a film under high temperature conditions, and it may happen that the voids are filled. Also, for example, chlorine generated in the reaction / production process of synthetic fibers remains mixed with synthetic fibers, and especially when Al is used for the electrode, it promotes corrosion and causes new problems, and it also complicates the processing process. There are drawbacks such as that Furthermore, it is not possible to obtain a homogeneous and stable separator (electrolytic paper), and it is difficult to obtain a sufficient increase in voids for activating the movement of ions even by the above-mentioned known means, which is a technical problem. However, there are drawbacks such as high raw material cost.

Further, starch, vegetable gum, semi-synthetic polymer, synthetic polymer and the like are added to the raw material suspension during the manufacturing process, which is a general means for increasing the tensile strength of paper, and the mixture is fixed on the fiber surface layer. Even the known means for increasing the bond strength between fibers cannot meet the more stringent requirement of low ESR (equivalent series resistance), that is, low impedance.

The separator (electrolytic paper) as described above
While improving itself, in such an electrolytic capacitor, the characteristics of the electrolytic solution play a major factor in determining the performance of the electrolytic capacitor.

In particular, with the recent miniaturization of electrolytic capacitors, as the anode foil or the cathode foil, one having a high etching rate has been used, and the resistivity of the capacitor body is increasing. As the electrolytic solution, one having a high electrical conductivity with a small resistivity (specific resistance) is always required.

In the conventional electrolytic solution, ethylene glycol is used as a main solvent, water (1% by weight to 30% by weight) is added thereto, and an ammonium salt of a carboxylic acid such as adipic acid or benzoic acid is further dissolved as an electrolyte. There is something I did.

The one using ammonium carboxylate as the electrolyte has a remarkably low specific resistance of 300 to 400 Ωcm as compared with the one using conventional boric acid as the electrolyte.

However, in the case of using this ammonium carboxylate, the specific resistance was limited to about 80 Ωcm even if various measures were taken.

That is, the specific resistance of the electrolytic solution can be reduced by increasing the amount of solute and increasing the amount of water added to another solvent such as ethylene glycol, but the concentration of water is 30%. When the content is more than 10% by weight, the electrolytic solution reacts with the electrode foil at a high temperature to generate a gas and raises the internal pressure of the electrolytic capacitor.

On the other hand, the required performances required for capacitors used by being mounted in various electronic / electrical products such as computers and audios, various vehicles, etc. are becoming more severe. It is essential to maintain low impedance characteristics in the low temperature range, and the low temperature (-4 ℃)
The low temperature characteristic value represented by the | Z | ratio (impedance ratio) at 0 ° C. is strongly required. Further, when a large amount of water is used together as a solvent component, problems such as freezing occur.

As described above, conventionally, the specific resistance could be reduced to about 80 Ωcm by adding water at a maximum of about 30% by weight, but further reduction of the specific resistance cannot be expected, and It was difficult to use in a wide temperature range from 105 ° C to -40 ° C.

The following are mentioned as prior arts related to the invention of the present application, but none of them describes or suggests the basic technical idea of the present invention. Hereinafter, Patent Documents 1 to 4 will be outlined (see Patent Document numbers below).

Patent Document 1 describes "a separator for an electrolytic capacitor, which is composed of a paper or a non-woven fabric in which a polyvinyl alcohol-based fiber having a low solubility is a main fiber and a polyvinyl alcohol-based fiber having a high solubility is bound as a binder. The main fiber has a monofilament fineness of 1 denier or less, and at least 10% by weight of the main fiber has a cross-section irregularly-shaped polyvinyl alcohol having a convex shape with 3 to 6 cross-sections. "Separator for electrolytic capacitor, characterized in that it is an alcohol-based fiber and the density of the separator is 0.25 g / cm ³ or less". Regarding the above-mentioned constitution and its function, "the point of the present invention is to use a PVA-based fiber having an irregular cross-section such as a Y-shaped cross-section as a main fiber constituting a separator and using a PVA binder as a binder. This is because the fibers are used, and even if the basis weight is greatly reduced, the entanglement effect of the fibers with the modified cross-section fibers and the adhesive effect with the homogenous binder are both increased. Although the details are unknown, we have obtained an extremely low density separator while maintaining the actual paper power, that is, a separator for electrolytic capacitors that has an unprecedented excellent effect of impedance reduction. Further, "hardly soluble in this specification" means that the electrolyte is impregnated during the manufacturing process of the paper and in the capacitor. It means that it is difficult to dissolve and does not need to maintain the form as a paper, which means that it is difficult to dissolve. ”“ In addition, an easily soluble binder fiber can be obtained without performing the acetalization treatment in the above manufacturing process. What is essential is that it can be dissolved in water at a moderately elevated temperature during the paper manufacturing process and can bond the main fibers, and such physical properties can be adjusted by adjusting the processing conditions in the stretching and heat treatment processes. Specifically, a fiber having a melting temperature in water of 50 to 90 ° C. ”is described.
As Example 1, 80 parts by weight of the main fiber A and 20 parts by weight of the binder fiber C were well dispersed in water, wet papermaking was carried out with a cylinder paper machine, and this wet paper was then introduced into a heating drum to form the binder fiber C. It is described that the main fibers A are melted by adhering to each other to form the separator of the present invention. That is, the separator described in Patent Document 1,
Basically, it is composed of main fibers including poorly soluble modified cross-section fibers and easily soluble binder fibers (PVA fibers), and the easily soluble binder fibers are added to water heated to 50 to 90 ° C during the papermaking process. It is in a molten state and serves to bond the main fibers. However, as described above, the PVA fiber has various properties such as solubility in water obtained by various conditions such as stretching and heat treatment in the manufacturing process, and thus the PVA fiber which is easily soluble therein is produced by the papermaking process. It has a characteristic of being dissolved in water in a state of being heated on the heating drum in the process, and is not dissolved in an electrolytic solution (organic solvent or mainly). Patent Document 1 does not specifically describe an electrolytic solution used in combination with the separator. Although only the electrolytic solution for impedance measurement is described, the electrolytic solution contains ethylene glycol as a solvent and ammonium adipate as a solute ([00
36]), the temperature rise (50-
It does not dissolve easily soluble PVA in water heated at 90 ° C. As described above, in Patent Document 1, the basic technical idea of the present invention is, "When a separator is constituted by fibers fixed with a binder soluble in an electrolytic solution and the separator is incorporated into the electrolytic solution. , Dissolving the binder in the electrolyte "is neither described nor suggested.

[0018] Japanese Patent Application Laid-Open No. 2004-242242 describes "an electrolytic capacitor constructed by interposing electrolytic paper between an anode foil and a cathode foil,
In particular, by using a new electrolytic paper that has a low density and significantly improved tensile strength, and the interfiber voids are not shielded, the short circuit defective rate is improved without adversely affecting the impedance characteristics. In addition, in order to improve productivity, "in an electrolytic capacitor in which electrolytic paper is interposed between an anode foil and a cathode foil, a purified solution of a paper strength enhancer is applied to electrolytic paper after paper making. "Electrolytic capacitor characterized by being impregnated and coated", and "the paper-strengthening agent is one or more selected from starch, vegetable gum, semi-synthetic polymer or synthetic polymer"
Specifically, it is described that vegetable gums such as guar gum, starches such as corn starch, semi-synthetic polymers such as dialdehyde starch, and synthetic polymers such as polyacrylamide resin are used. Further, regarding the action of the paper strengthening agent, "The purified solution of the paper strength enhancing agent applied by impregnation effectively fixes the paper strength enhancing agent at the contact points of the fibers in the paper layer, and the bond strength between the fibers. In addition, the strength of the single fiber itself can be increased because it penetrates into the inside of the fiber, so that the electrolytic paper has a higher bonding strength of the fiber while maintaining the inter-fiber voids. There is no over-beating to generate microfibrils, and there is no shielding of fiber gaps by film formation of heat-sealed fibers,
It has a low density, is thin, and has a high tensile strength. " As for the electrolytic solution, it is merely described that the "predetermined electrolytic solution" is used. As described above, in Patent Document 2, as a paper reinforcing agent,
Although "polyacrylamide" mentioned as the binder of the present invention is exemplified, there is no description about the composition of the electrolytic solution in the first place, and there is no suggestion about the solubility of the paper enhancing agent in the electrolytic solution. The basic technical idea of the present invention shown above is neither described nor suggested.

[0019] Patent Document 3 describes a separator having low density paper and low impedance, in which main fibers are bound with a polyvinyl alcohol-based binder, and the polyvinyl alcohol (PVA) is a hydrophilic polymer. It is stated that there is. However, the PVA described in the cited document 3 is used for the same purpose as that described in the above-mentioned Patent Document 1, and when the separator fiber is made into paper to form the separator, Only the use of PVA which is soluble in water at high temperature (60-98 ° C) is disclosed. Patent Document 1 discloses a basic technical concept of the present invention, "a separator is composed of fibers fixed by a binder soluble in an electrolytic solution, and when the separator is incorporated into the electrolytic solution, the binder is formed by the electrolytic solution. Is not described or suggested.

Patent Document 4 describes "an electrolytic solution for electrolytic capacitors comprising inorganic oxide colloidal particles surface-modified with a solvent, a solute and an organic substance", and "an organic solvent whose solvent is mainly ethylene glycol or γ-butyrolactone". "It is a solvent", and in that case, "the electrolytic solution may contain water for the purpose of improving the chemical conversion property. The content of this water is preferably 0.01 to 30% by weight. In the range of. However, in the cited document 4, which is a basic technical idea of the present invention, "a separator is composed of fibers fixed with a binder soluble in an electrolytic solution, and when the separator is incorporated into the electrolytic solution, the electrolytic solution is Dissolving the binder with "is neither described nor suggested.

[0021]

[Patent Document 1] JP-A-6-29155

[Patent Document 2] Japanese Patent Laid-Open No. 8-273984

[Patent Document 3] JP-A-6-163324

[Patent Document 4] Japanese Unexamined Patent Publication No. 10-241999

[0022]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic capacitor having low impedance, excellent low temperature characteristics, good life characteristics, improved short circuit defect rate and improved productivity. The purpose is to do.

[0023]

The present invention is an electrolytic capacitor for achieving the above object, comprising an electrolytic solution and a separator containing fibers fixed with a binder soluble in the electrolytic solution, In the electrolytic capacitor, the electrolytic solution contains an electrolyte and an electrolytic solvent containing water and an organic solvent, and the water concentration in the electrolytic solvent is 20% by weight or more and less than 35.3% by weight. Further, the present invention is an electrolytic capacitor comprising an electrolytic solution and a separator containing fibers fixed with a binder soluble in the electrolytic solution, wherein the electrolytic solution contains an electrolyte and an electrolyte solvent containing water and an organic solvent. An electrolytic capacitor in which the water concentration in the electrolyte solvent is 20% by weight or more and less than 35.3% by weight, and the specific resistance of the electrolytic solution at 30 ° C. is 40 Ω · cm or less.

By constructing the separator disposed between the metal foils such as aluminum forming the electrodes as described above, the binder can fix the fibers to each other and maintain sufficient strength in the manufacturing process. It is possible to prevent paper breakage in the element winding process and improve the winding productivity. Further, as a result, it is possible to prevent localization and uneven distribution of fibers even in the form of an element, so that it is possible to promote thinning and realize low impedance, and at the same time, reduce the short circuit defect rate.

Further, when considering the function,
The binder effectively functions to maintain strength during the process of winding the separator between the electrodes, molding, impregnating the device with the electrolyte, and packaging the case. After a period of time that can be determined by preparing the combination of, the intermolecular expansion is brought about by the action of the solvent of the electrolytic solution. It is considered that the binder polymer in that state weakens the bonds between the cellulose fibers and increases the voids.

As another aspect, the present invention includes a separator for an electrolytic capacitor, which includes fibers fixed by a binder soluble in an electrolytic solution, and an electrolytic solution solvent containing an organic solvent and water having a water concentration of 20 to 20. It is also possible to set it to 80% by weight. It is possible to make use of the decrease in the specific resistance, which is an excellent characteristic of the electrolytic solution using a solvent containing a high concentration of water, and it is also possible to achieve the operational effects of the separator.

Further, in the invention, in each of the above inventions, the density of the separator (measured at the time of molding the separator) is 0.
The amount is 5 g / cm ³ or less. That is, when the separator density is 0.5 g / cm ³ or less, the density of the cellulose fibers is 1.5 g / cm ³ , so the porosity of the separator {[1- (separator density / cellulose density)].
X100%} is 67% or more, and the electrolyte solution is sufficiently contained in the increased voids. Therefore, with the above-mentioned structure, the strength required for molding (1.1 kg / 15
(mm or more), the separator density in the electrolytic capacitor can be minimized to lower the impedance.

Furthermore, the present invention uses various ionic and nonionic binders as binders in the above inventions, among which water-soluble polyvinyl alcohols, polyacrylamides, polyacrylic acids, etc. are particularly preferred. Those using a polymer have excellent capacitor characteristics.

Further, the present invention includes the separator according to each of the above inventions, contains an organic solvent and water as a solvent of the electrolytic solution,
The water concentration in the organic solvent is 20 to 80% by weight of the total solvent,
The organic solvent is an electrolytic capacitor containing at least one selected from protic and aprotic solvents.

Further, the present invention includes the separator according to each of the above inventions, contains an organic solvent and water as a solvent of the electrolytic solution,
The water concentration in the organic solvent is 20 to 80% by weight of the total solvent,
The organic solvent contains at least one kind selected from protic and aprotic solvents, and at least one kind selected from carboxylic acids or salts thereof and inorganic acids or salts thereof as an electrolyte of the electrolytic solution. It is an electrolytic capacitor including the above.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The separator of the present invention preferably uses, as a fibrous material, cellulosic fibers such as wood kraft pulp, coniferous wood pulp, Manila hemp pulp and sisal hemp.

In consideration of strength and density reduction, other fiber materials, thermoplastic fibers such as vinylon binder fiber, polyethylene fiber, polypropylene fiber, nylon fiber, etc. are mixed to form paper, and then the thermoplastic fibers are fused. Means for increasing the tensile strength are known, and in addition to natural plant fibers, viscose rayon fibers, polypropylene fibers, polyimide fibers, synthetic fibers such as aramid fibers, glass fibers,
Low density, including inorganic fibers such as alumina silica
Attempts have been made to obtain paper with a high porosity,
As described above in the section of the prior art, various problems occur when mixing synthetic fibers, so it is not a good idea to use a large amount.

It is most preferable to use one or more natural vegetable fibers which have few problems as described above and which are compatible with water which is a solvent component of the electrolytic solution.

The electrolytic paper can be produced by a conventional papermaking method. For example, a conventionally used papermaking machine such as a cylinder papermaking machine having one or more cylinder net butt portions of the above fiber material. To make paper.

The binder can be mixed with the fiber material in advance during the papermaking, but it is not preferable because it requires an extra material and complicates the process such as the drying process.
Preferably, the electrolytic paper after papermaking is dried and then impregnated with a binder to fix the fibers.

The impregnated amount may be determined according to the strength at the time of manufacture and the required characteristics of the electrolytic capacitor after manufacture, but is about 0.05% by weight to 5.0% by weight with respect to the dried electrolytic paper. is there. The tensile strength of electrolytic paper is 1.1kg / 15mm
The above is one guideline. The thickness of the electrolytic paper can be appropriately selected, but is usually about 40 to 60 μm.

The density of the electrolytic paper is 0.5 g / cm ³ or less of what is desired, 0.20~0.35g / cm ^3, it is also possible further to less than 0.20 g / cm ^3, low Desirable for impedanceization.

The binder can be used as long as it is soluble in the solvent component of the electrolytic solution. Particularly, when water and an organic solvent are used as the solvent component of the electrolytic solution, water is 20 to 80.
%, Preferably 30-80% by weight, more preferably 35.
In the case of containing 3 to 80% by weight, and most preferably 45 to 80% by weight, various starches, carboxymethyl cellulose, various gums and the like can be used, but strength, retention stability, shape retention and easy handling From the viewpoint of maintaining the fiber form in the electrolytic solution and ensuring low impedance characteristics, water-soluble polymers such as polyvinyl alcohol, polyacrylamide and polyacrylic acid are excellent. The amount of the binder used varies depending on the type, but is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the separator.

Electrolytic paper (isolation paper) fixed with a binder
Is a conventional method, in which a high-purity aluminum foil is etched, the surface of which is anodized and an anode foil and an aluminum foil which is opposite to the foil are interposed and wound up, and then the element is wound. The electrolytic solution is impregnated, and this element is housed in an aluminum case and sealed with an elastic sealing body to obtain an electrolytic capacitor.

The electrolytic solution to be impregnated is another feature of the present invention.

The conventional electrolytic solution has ethylene glycol as a main solvent, to which water (1% by weight to 30% by weight) is added,
Further, many electrolytes have dissolved ammonium carboxylates such as adipic acid and benzoic acid.

As already described in the embodiments of the invention, even in the case where ammonium carboxylate is used as the electrolyte, the specific resistance is limited to about 80 Ωcm.

However, the solvent of the electrolytic solution contains an organic solvent and water, and the concentration of water in the organic solvent is 20 to 8% of the total solvent.
0% by weight, the organic solvent contains at least one selected from the group consisting of protic and aprotic solvents,
Moreover, in a configuration including each separator according to the present invention, or containing an organic solvent and water as a solvent of the electrolytic solution, the water concentration in the organic solvent is 20 to 80 wt% of the total solvent, the organic solvent is a proton A solvent containing at least one selected from the group consisting of aprotic and aprotic solvents, and containing at least one selected from a carboxylic acid or a salt thereof and an inorganic acid or a salt thereof as the electrolyte of the electrolytic solution, By obtaining the electrolytic capacitor, it is possible to obtain an electrolytic capacitor having low impedance, excellent low temperature characteristics, and good life characteristics.

As the organic solvent, a protic solvent and an aprotic solvent can be used. An alcohol compound can be given as an example of a typical proton-based solvent.

Specific examples of the alcohol compound include monohydric alcohols such as ethyl alcohol, propyl alcohol and butyl alcohol, dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol and propylene glycol, and triglycerides such as glycerin. Mention may be made of polyhydric alcohols.

Examples of the aprotic solvent include intramolecularly polarized compounds such as lactone compounds represented by γ-butyrolactone. As the organic solvent, one or more selected from a protic solvent and an aprotic solvent can be used. You may use plural kinds of protonic solvents,
A plurality of kinds of aprotic solvents may be used, or a mixed system of a protic solvent and an aprotic solvent may be used.

As described above, the solvent in the electrolytic solution of the present invention is a mixture of an organic solvent and water. In the present invention,
By using such a mixed solvent, the freezing point of the solvent is lowered, thereby improving the impedance characteristics of the electrolytic solution at low temperature, and the good low-temperature characteristics shown by the low impedance ratio at low temperature and room temperature. Can be realized. The content of water in the electrolytic solution is preferably 20 to 80% by weight, and the balance is an organic solvent. Whether the water content is less than 20% by weight or more than 80% by weight,
The degree of depression of the freezing point of the electrolytic solution becomes insufficient, and it becomes difficult to obtain good low-temperature characteristics of the electrolytic capacitor. A more preferable amount of water in the solvent is 30 to 80% by weight,
A more preferable amount of water is 35.3 to 80% by weight, and the most preferable amount is 45 to 80% by weight.

As the electrolyte in the electrolytic solution, one or more selected from carboxylic acids, salts of carboxylic acids, inorganic acids and salts of inorganic acids can be used. Examples of the carboxylic acid that can be used include formic acid, acetic acid, propionic acid, butyric acid, p-nitrobenzoic acid, salicylic acid and monocarboxylic acids typified by benzoic acid, malonic acid, succinic acid, glutaric acid, adipic acid and fumaric acid. Acid, maleic acid,
Dicarboxylic acids represented by phthalic acid and azelaic acid are included, and carboxylic acids having a functional group such as an OH group such as citric acid and oxybutyric acid can also be used.

Examples of usable inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, sulfamic acid and the like. As salts of carboxylic acids or inorganic acids, in addition to ammonium salts, sodium salts, potassium salts, amine salts, alkyl ammonium salts, etc. can be used.
Of these, it is more preferable to use the ammonium salt. Moreover, when an inorganic acid or a salt thereof is used as the electrolyte, it is expected that the freezing point of the electrolytic solution will be lowered, and therefore it is considered that this will contribute to further improvement of the low temperature characteristics of the electrolytic solution.

The amount of electrolyte used in the electrolytic solution of the present invention depends on the characteristics required for the electrolytic solution, the type of solvent used,
It may be appropriately determined according to conditions such as the type of electrolyte used.

As the additive, one or more selected from gluconic acid, lactone of gluconic acid, chelating agent, 2-hydroxybenzyl alcohol, L-glutamic acid diacetic acid or a salt thereof, nitro compound, sugar and the like are used. can do. The addition amount of these additives is an optimum addition amount depending on the combination of the additives and the composition of the electrolytic solution. Since the amount of addition at this time is determined by the characteristics of the added substance, it may be about several wt% or less of the electrolytic solution or 1 wt% or less. By combining these additives, it is possible to avoid reaction with the electrode at high temperature, reduce specific resistance at low temperature, and improve capacitor life.

For example, when gluconic acid or a lactone of gluconic acid is added, even if the amount of water used in the solvent in the electrolytic solution is 30% by weight or more in the solvent, a gas based on the reaction between the electrolytic solution and the electrode at high temperature Can be avoided, and the specific resistance can be reduced. Further, by adding the chelate compound, it is possible to prolong the service life by suppressing the hydration reaction of the electrode foil. In addition, by adding 2-hydroxybenzyl alcohol, L-glutamic acid diacetic acid or a salt thereof, a nitro compound, and a saccharide, the same effect can be obtained. By adding these plural components in combination, a synergistic effect in improving the characteristics of the electrolytic capacitor can be achieved.

Examples of the nitro compound include at least one nitro compound selected from the group consisting of nitrophenol, nitrobenzoic acid, nitroacetophenone and nitroanisole.

As the chelate compound, ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid monohydrate (CyDTA), dihydroxyethylglycine (DHE).
G), ethylenediaminetetrakis (methylenephosphonic acid) (EDTPO), diethylenetriamine-N, N,
N ', N ", N" -pentaacetic acid (DTPA), diaminopropanoltetraacetic acid (DPTA-OH), ethylenediaminediacetic acid (EDDA), ethylenediamine-N, N'-bis (methylenephosphonic acid) 1/2 hydrate Thing (EDDP
O), glycol ether diamine tetraacetic acid (GEDT
A) etc. can be illustrated.

Examples of the sugars include glucose, fructose, xylose, galactose and the like.

Besides these additives, additives conventionally used in the field of aluminum electrolytic capacitors or other electrolytic capacitors may be further added.

[0057]

EXAMPLES (Examples 1 to 4 and Comparative Examples 1 and 2) Examples of the present invention will be described below. Ethylene glycol 4
5% by weight, 40% by weight of water, ammonium adipate 1
4.4 wt%, ethylenediaminetetraacetic acid 0.5 wt%,
The point that 0.1% by weight of D-gluconic acid-δ-lactone is used as the electrolytic solution and the point that the separator (electrolytic paper) is composed of cellulosic fibers are common to the examples and comparative examples. A conventional cellulosic separator that does not use a binder that dissolves in a solvent (only the density is changed in Conventional Examples 1 and 2) and the binder shown in the table (the amount of the binder used is 100% by weight of each separator). The initial characteristics of the capacitors were compared by using the cellulosic separator of the present invention (2 parts by weight based on 1 part by weight) (the density was changed between Examples 1 and 2 and Examples 3 and 4). In addition, the low temperature (-
Impedance ratio expressed as the ratio of the impedance at 40 ° C to the impedance at room temperature (20 ° C) (|
Z | ratio) was measured at 120 Hz and 100 kHz. Impedance and E.I. S. R and (equivalent series resistance) are values at a measurement temperature of 25 ° C. The measurement results are shown in Table 1.

[0058]

[Table 1]

No difference in separator density was observed between Comparative Example 1 and Examples 1 and 2 in Table 1 and between Comparative Example 2 and Examples 3 and 4, and almost no difference was found in the initial capacitor capacity. There is no difference.

However, when tan δ is compared with those of the same density, the example is smaller than the comparative example and is excellent in impedance characteristics. Although the separators of Examples 1 and 2 have a higher density than the separator of Comparative Example 2, the initial tan δ, impedance, and E.V. S. R. Is small. It can be said that this shows that the strength can be sufficiently maintained in the manufacturing process, and that the characteristics after mounting can be excellent, that is, the characteristics with a long life can be obtained.

Among them, those using polyvinyl alcohol and polyacrylamide as the binders of Examples 3 and 4 had a small separator density and had a low initial impedance and E.I. S. R. The value of is extremely small, indicating that the initial characteristics of the capacitor are excellent. There is no substantial difference in the initial leakage current between the comparative examples and the examples.

Further, in the capacitor using the electrolytic solution of the present invention, it was found that the Z ratio was small, and particularly 100
It can be seen that the Z ratio at a high frequency of kHz is suppressed smaller than that of the comparative example. This indicates that the electrolytic capacitor using the electrolytic solution of the present invention exhibits good low temperature characteristics over a wide frequency range.

The composition of the electrolytic solution which exhibits particularly excellent electrolytic capacitor characteristics in combination with the separator of the present invention is shown in Table 2 below as a composition example together with a conventional example.

[0064]

[Table 2]

[Table 3]

As a preferable composition example in the present invention, a solvent obtained by combining an organic solvent and a large amount of water, and at least one or more electrolytes selected from the group consisting of a carboxylic acid or a salt thereof and an inorganic acid and a salt thereof are used as an electrolytic solution. As examples of basic components, examples were given in which various additive components capable of obtaining excellent additive addition effects were combined. Composition examples 1 and 2
Is an example of a combination of gluconolactone and a chelate compound as an additive (in the case of this combination, 0.01 to 3% by weight in the electrolytic solution is usually preferable), and Composition Examples 3 and 4.
Is an example of a combination of gluconolactone and a saccharide (in this combination, 0.01 to 5% by weight is usually preferable in the electrolytic solution), and Composition Examples 5 and 6 are gluconolactone and glutamic acid diacetic acid, respectively. And a combination of gluconolactone and hydroxybenzyl alcohol (in the case of these combinations, it is usually 0.01 to 5 in the electrolytic solution).
Weight percent is preferred. ), And Composition Examples 7 and 8 are examples in which gluconolactone and a nitro compound are combined (in the case of this combination, 0.01 to 3% by weight is usually preferable in the electrolytic solution).
Is.

[0066]

As described above, the electrolytic capacitor constituted by the separator according to the present invention and the specific electrolytic solution makes it possible to obtain an electrolytic capacitor having low impedance, excellent low temperature characteristics and excellent life characteristics.

Although the present invention has been variously described with reference to the preferred embodiments, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

Claims (2)

[Claims] 1. An electrolytic capacitor comprising an electrolytic solution and a separator containing fibers fixed with a binder soluble in the electrolytic solution, wherein the electrolytic solution contains an electrolyte and an electrolyte solvent containing water and an organic solvent. The concentration of water in the electrolyte solvent is 2
An electrolytic capacitor containing 0% by weight or more and less than 35.3% by weight. 2. An electrolytic capacitor comprising an electrolytic solution and a separator containing fibers fixed with a binder soluble in the electrolytic solution, the electrolytic solution containing an electrolyte and an electrolytic solvent containing water and an organic solvent. The concentration of water in the electrolyte solvent is 2
0% by weight or more and less than 35.3% by weight of the electrolyte solution at 30 ° C.
An electrolytic capacitor having a specific resistance of 40 Ω · cm or less.